Aim The aim of the study was to examine whether patient-provider communication interacts with treatment outcomes to influence patients' risk perception. Background Medical uncertainties and risks are among the most serious problems faced by patients. This is exacerbated by communication failure in patient-provider relationships and poor treatment outcomes. However, we do not know how communication and treatment outcomes shape patients' risk perception and concern about uncertainty. Design The study is a two-by-two between-subjects design. Methods Two studies were conducted and data were collected in 2019. Each study used a different research design and different samples: Study 1 used a scenario experiment with 120 undergraduate students; and Study 2 surveyed 200 inpatients in clinical settings. Results The convergent results found a significant interaction between patient-provider communication and treatment outcome on the perception of medical risks among the participants. Conclusion Patient-provider communication interacts with treatment outcome to influence patients' perceived risk about uncertainties for healthcare. Clinicians and nurses should be aware of the effects of patient-provider communication on patients' risk perception in their concerns about the uncertainties of treatment and pay much more attention to good healthcare relationship building in addition to the improvement of objective treatment outcome.